Organic electroluminescent device

ABSTRACT

Disclosed is an organic electroluminescent device including a substrate, a first and a second electrode, and an emitting layer formed between the first electrode and the second electrode. The emitting layer includes a plurality of materials which is a blue emitting material using a following chemical formula as dopant. 
     
       
         
         
             
             
         
       
     
     In this case, at least one of A 1  and A 2  is selected from a substituted or non-substituted aromatic group, a heterocyclic group, an aliphatic group, and hydrogen.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of application Ser. No. 10/743,778,filed Dec. 24, 2003. This invention claims the benefit of Korean PatentApplication No. 10-2002-0083279 filed in Korea on Dec. 24, 2002 andKorean Patent Application No. 10-2003-0020465 filed in Korea on Apr. 1,2003, which are hereby incorporated by reference in their entity.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an organic luminescent device, and moreparticularly, to a blue emitting material of an emitting layer.

2. Description of the Related Art

Recently, with the trend of a large sized display, a request of a flatdisplay that occupies a small area has been increased. One example ofthe flat display is an organic electroluminescent device also called asan organic light emitting diode (OLED). And, technology for the organicelectroluminescent display is developed rapidly, whereby variousprototypes have been in market already.

The organic electroluminescent device emits light in a manner thatelectric charges are injected in an organic layer formed between ananode and a cathode so as to form a pair of electron and hole togenerate an exciton and an excited state of the exciton falls to aground state so as to emit light.

The organic electroluminescent device is not only formed on a flexibletransparent substrate such as a plastic but also operated at a lowervoltage (less than 10V) compared to a plasma display panel or aninorganic electroluminescent display.

Also, the organic electroluminescent device has advantages in that powerconsumption is reduced and various colors are available.

Moreover, the organic electroluminescent device enables to express threecolors including green, blue, and red. Therefore, many concerns arefocused on the organic electroluminescent device as the next generationfull color display.

The organic electroluminescent device may be realized to emit blue,green, or red light in accordance with a material forming the emittinglayer.

Particularly, the emitting layer for blue luminescence is a hostemploying materials such as PBD and DPVBi and is fabricated by doping1-3% of materials such as perylene, coumarine, and pyrene as a dopant.

However, it is a biggest problem in realizing blue luminescence of theorganic electroluminescent device that a degree of color purity and theluminescence efficiency are lowered.

The conventional blue emitting materials emit light with a longwavelength during emission and had a problem of lowering the degree ofcolor purity and the luminescence efficiency, and even more lowered athigh doping density.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to an organicelectroluminescent device that substantially obviates one or moreproblems due to limitations and disadvantages of the related art.

An object of the present invention is to provide an organicelectroluminescent device.

Additional advantages, objects, and features of the invention will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objectives and other advantages of the invention may berealized and attained by the structure particularly pointed out in thewritten description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described herein, anorganic luminescent device includes a substrate; a first and secondelectrodes formed on the substrate; an emitting layer formed between thefirst electrode and the second electrode, the emitting layer having aplurality of materials and being a blue emitting material using achemical formula 1 as a dopant.

In this case, at least one of A₁ and A₂ is selected from a substitutedor non-substituted aromatic group, a heterocyclic group, an aliphaticgroup, and hydrogen.

Wt. % of the material in the chemical formula 1 is 0.1-49.9 wt. % of atotal weight of the emitting layer.

Material forming the emitting layer together with the material of thechemical formula 1 is formed as a structure of a following chemicalformula 2.B1-X—B2  [Chemical formula 2]

Wherein, the X is selected from a group consisting of naphthalene,anthracene, phenanthrene, pyrene, perylene, and quinoline and at leastone of the B1 and B2 is selected from a group consisting of aryl,alkylaryl, alkoxyaryl, arylaminoaryl and alkylaminoaryl.

At least one of the B1, B2 is selected from phenyl, biphenyl, pyridyl,naphthyl, tritylphenyl, biphenylenyl, anthryl, phenanthryl, pyrenyl,perylenyl, quinolyl, isoquinolyl, fluorenyl, terphenyl, tolyl, xylyl,methylnaphthyl, and hydrogen.

At least one of the A1 and A2 is selected from a substituted ornon-substituted phenyl, a substituted or non-substituted biphenyl, asubstituted or non-substituted pyridyl, a substituted or non-substitutednaphthyl, a substituted or non-substituted quinolyl, a substituted ornon-substituted isoquinolyl, a substituted or non-substituted fluorenyl,a substituted or non-substituted terphenyl, methyl, ethyl, propyl,i-propyl, and t-buthyl.

The substituent of each substituted A1 and A2 is at least one andselected from methyl, ethyl, propyl, i-propyl, t-butyl, cyclohexyl,methoxy, ethoxy, propoxy, butoxy, dimethylamino, trimethylsilyl,fluorine, chroline, phenoxy, tolyloxy, dimethylamino, diethylamino,diphenylamino, and triphenylsilyl.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts.

In the present invention, the emitting layer formed between a firstelectrode and a second electrode includes a plurality of materials and ablue material using a following chemical formula as a dopant.

In this case, at least one of A₁ and A₂ is selected from a substitutedor non-substituted aromatic group, a heterocyclic group, an aliphaticgroup, or hydrogen.

A wt. % of the material in the chemical formula 1 is 0.1˜49.9 wt % amonga total weight of the emitting layer. The material forming the emittinglayer with the chemical formula 1 is formed as a structure of afollowing chemical formula 2.B1-X—B2  [Chemical formula 2]

In this case, X is selected from a group consisting of naphthalene,anthracene, phenanthrene, pyrene, perylene, and quinoline. At least oneof the B1 and B2 may be selected from a group consisting of aryl,alkylaryl, alkoxyaryl, arylaminoaryl and alkylaminoaryl.

Also, at least one of the B1 and B2 may be selected from a groupconsisting of phenyl, biphenyl, pyridyl, naphthyl, tritylphenyl,biphenylenyl, anthryl, phenanthryl, pyrenyl, perylenyl, quinolyl,isoquinolyl, fluorenyl, terphenyl, tolyl, xylyl, methylnaphthyl, andhydrogen.

In this case, the material forming the emitting layer together with thechemical formula 1 is one of following chemical formulas.

Also, in a case of the chemical formula 1, at least one of the A1 and A2may be selected from a substituted or non-substituted aromatic group, aheterocyclic group, an aliphatic group, and hydrogen.

Particularly, at least one of A1 and A2 may be selected from asubstituted or non-substituted phenyl, a substituted or non-substitutedbiphenyl, a substituted or non-substituted pyridyl, a substituted ornon-substituted naphthyl, a substituted or non-substituted quinolyl, asubstituted or non-substituted isoquinolyl, a substituted ornon-substituted fluorenyl, a substituted or non-substituted terphenyl,methyl, ethyl, propyl, i-propyl, and t-buthyl.

In this case, each substituent of the substituted A1 and A2 is at leastone and selected from alkyl, alkoxy, alkylamino, alkylsilyl, halogen,aryl, aryloxy, arylamino, arylsilyl, and hydrogen.

For example, the substituent of the A1 and A2 may be selected frommethyl, ethyl, propyl, i-propyl, t-butyl, cyclohexyl, methoxy, ethoxy,propoxy, butoxy, dimethylamino, trimethylsilyl, fluorine, chlorine,phenoxy, tolyloxy, dimethylamino, diethylamino, diphenylamino, andtriphenylsilyl.

Particularly, at least one of the substituted or non-substituted A1 andA2 may be one of the following chemical formulas.

The blue emitting material having the substituent of the presentinvention may be one of the following chemical formulas.

According to the organic electroluminescent device,N,N′-Bis-(4-tert-butyl-phenyl)-N,N′-di-pyridin-2-yl-pyrene-1,6-diamineemployed as the blue emitting material is compounded as follows.

(1) Synthesis of 1,6-Dibromopyrene

First, pyrene (10 g, 0.0049 mol) is dissolved into CCl₄ (300 mL) in a3-necks-r.b.f. And, Br₂(17.38 g, 0.108 mol)

CCl₄(50 mL) are put into a dropping funnel provided at the round-floorflask and slowly dropped in the round-floor flask for 4 hours. N₂ isadded to and HBr is removed from the solution. When the process isfinished, the solution is stirred under N₂ current for one hour andformed sediment is filtered.

When the sediment is recrystallized by toluene, a green solid matter(6.05 g, 34%) of 1,6-Dibromopyrene and a white solid matter of1,8-Dibromopyrene (5 g, 28%) are obtained.

(2) Synthesis of N,N,N′,N′-Tetraphenyl-pyrene-1,6-diamine

First, 1,6-Dibromopyrene (3 g, 0.0083 mol), Diphenylamine (4.23 g, 0.025mol), BINAP([2,2′-Bis(diphenylphosphino)-1,1′-binaphthyl])(0.052 g, 1%mol), Pd(OAC)₂[Palladium(∥)acetate](0.019 g, 1% mol) andNaO^(t)Bu[Sodium tert-butoxide](2.3 g, 0.029 mol) are dissolved intotoluene (80 mL) in 2-necks-r.b.f. so as to be refluxed.

When the reaction is finished, the 2-necks-r.b.f. is cooled at a normaltemperature and about 40 ml of toluene, that is, a reaction solvent isremoved by distillation under reduced pressure.

When methanol (100 ml) is added to the solution from which toluene 40 mlis removed, sediment is generated.

When the sediment is filtered, a yellow solid matter ofN,N,N′,N′-Tetraphenyl-pyrene-1,6-diamine (3.22 g, 72%) is obtained.

(3) Synthesis of (4-Bromo-phenyl)-trimethyl-silane

First, a dropping funnel is provided at the 3-necks-r.b.f. and theround-floor flask is dried under decompression. 1,4-Dibromobenzene (12.7g, 0.053 mol) and the dried diethylether (300 mL) are dissolved in theround-floor flask.

A dryice bath is provided at the round-floor flask, n-BuLi (33.58 mL,0.0537 mol) is put into the dropping funnel and n-BuLi is slowlydropped, and a temperature is slowly raised from −78° C. to 0° C.

Next, chloro trimethylsilane (7.51 mL, 0.059 mol) is slowly dropped at0° C. and then the temperature is raised again to the normal temperaturefor over a period of one hour.

When the reaction is finished, sediment is extracted by usingdiethylether and water is removed from the result by using MgSO₄.

And then, after solvent is removed from the result, when the solvent isfractionally distilled under decompression,(4-Bromo-phenyl)-trimethyl-silane (11.3 g, 92%) is obtained.

(4) Synthesis of (4-tert-Butyl-phenyl)-(4-trimethylsilanyl-phenyl)-amine

4-tert-Butyl-phenylamine (1.2 mL, 0.0076 mol),(4-Bromo-phenyl)-trimethyl-silane (1 g, 0.0044 mol), BINAP (0.03 g, 1%mol), Pd(OAc)₂(0.01 g, 1% mol) and NaO^(t)Bu (1.5 g, 0.016 mol) aredissolved into toluene (50 mL) in the 2-necks-r.b.f. so as to berefluxed for about 2 hours.

When the reaction is finished, the 2-necks-r.b.f. is cooled and toluene,which is reaction solvent, is removed.

Next, when the sediment is filtered, the white solid matter such as(4-tert-Butyl-phenyl)-(4-trimethylsilanyl-phenyl)-amine (1.12 g, 86%) isobtained.

(5) Synthesis ofN,N′-Bis-(4-tert-butyl-phenyl)-N,N′-bis-(4-trimethylsilanyl-phenyl)-pyrene-1,6-diamine

(1,6-Dibromopyrene)(0.787 g, 0.0022 mol),(4-tert-Butyl-phenyl)-(4-trimethylsilanyl-phenyl)-amine)(1.56 g, 0.00525mol), BINAP (0.054 g, 4% mol), Pd(OAc)₂(0.015 g, 3% mol) and NaO^(t)Bu(0.93 g, 0.0096 mol) are dissolved in toluene (40 mL) so as to berefluxed for 24 hours.

When reaction is finished, the round-floor flask is cooled and resultmaterial is extracted by using water and methylene chloride aftertoluene, that is, the reaction solvent is removed.

And then, water is removed from the result by using MgSO₄ and methylenechloride is removed by decompression, and silica gel chromatography isseparated by using n-hexane:methylene chloride (6:1).

When the solvent is removed from the result and a solid matter isfiltered by using nucleic acid, yellow solid matter such as(N,N′-Bis-(4-tert-butyl-phenyl)-N,N′-bis-(4-trimethylsilanyl-phenyl)-pyrene-1,6-diamine)(1.09g, 63%) is obtained.

(6) Synthesis of N,N′-Diphenyl-N,N′-di-pyridin-2-yl-pyrene-1,6-diamine

(1,6-Dibromopyrene) (1.2 g, 0.0033 mol),(Phenyl-pyridin-2-yl-amine)(1.36 g, 0.008 mol), BINAP (0.083 g, 4% mol),Pd(OAc)₂(0.022 g, 3% mol) and NaO^(t)Bu (1.28 g, 0.013 mol) aredissolved in toluene (50 mL) in the 2-necks-r.b.f. so as to be refluxedfor 24 hours.

When the reaction is finished, solid matter is generated.

When 50% of toluene is removed from the solid matter, and methanol (70ml) is added to the solid matter, which then is filtered, yellow solidmatter (N,N-Diphenyl-N,N-di-pyridin-2-yl-pyrene-1,6-diamine)(0.81 g,45%) is obtained.

(7) Synthesis of (4-terr-Butyl-phenyl)-pyridin-2-yl-amine

(4-tert-Butyl-phenylamine) (1.2 mL, 0.0076 mol), (2-Bromo pyridine)(1mL, 0.01 mol), BINAP (0.06 g, 4% mol), Pd(OAc)₂(0.02 g, 3% mol) andNaO^(t)Bu (1.5 g, 0.016 mol) are dissolved in toluene (50 mL) in the2-necks-r.b.f. so as to be refluxed for 24 hours.

When the reaction is finished, the 2-necks-r.b.f. is cooled and toluene,that is, reaction solvent is removed. Result material is extracted byusing water and methylene chloride, methylene chloride is removed underdecompression after water is removed by using MgSO₄.

Silica gel short column is generated by methylene chloride, sediment isformed by using nucleic acid. When the sediment is filtered, white solidmatter such as 4-tert-Butyl-phenyl)-pyridin-2-yl-amine (1.32 g, 73%) isobtained.

(8) Synthesis ofN,N′-Bis-(4-tert-butyl-phenyl)-N,N′-di-pyridin-2yl-pyrene-1,6-diamine

1,6-Dibromopyrene (1 g, 0.0028 mol), (4-tert-Butyl-phenyl)-pyridin-2-ylamine (1.51 g, 0.0067 mol), BINAP (0.07 g, 4% mol), Pd(OAc)₂(0.02 g, 3%mol)

NaO^(t)Bu (1.18 g, 0.012 mol) are dissolved in toluene (45 mL) in the2-necks-r.b.f. so as to be refluxed for 24 hours.

When the reaction is finished, solid matter is generated. 50% of tolueneis removed from the solid matter, which is then filtered after methanol(70 mL) is added thereto. When the solvent is removed by silica gelshort column by using methylene chloride,(N,N′-Bis-(4-tert-butyl-Phenyl)-N,N′-di-pyridin-2-yl-pyrene-1,6-diamine)(0.99g, 60%) is obtained.

Hereinafter, a preferred embodiment of the organic electroluminescentdevice will be described according to the present invention.

EMBODIMENT

An ITO glass is patterned so as to have a size of 3 mm×3 mm. Thepatterned ITO glass is then cleaned.

A substrate is loaded on a vacuum chamber of which basic pressure is setup as 1×10⁻⁶ torr, CuPC(200 Å), NPB(500 Å), a light-emitting layer (300Å), Alq₃(500 Å), LiF(5 Å), and Al(1,000 Å) are deposited on the ITO inorder.

In this case, material in a following drawing is employed as a firstHOST of the emitting layer and a mixing ratio of the host and dopant is1:0.01.

First Embodiment

When about 1 mA of electric current is flown by using dopant having achemical formula of S-26, brightness shows about 3.2 cd/A, whereby CIE(Commision Internationale de L′Eclairage) x=0.146, y=0.205.

Second Embodiment

When about 1 mA of electric current is flown by using dopant having achemical formula of S-28, brightness shows about 3.4 cd/A, whereby CIE(Commision Internationale de L′Eclairage) x=0.15, y=0.196.

Comparative Embodiment

ITO (Indium Tin Oxide) glass is patterned so as to have a size of 3 mm×3mm. The patterned ITO glass is then cleaned.

A substrate is loaded on a vacuum chamber of which basic pressure is setup as 1×10⁻⁶ torr, and such an organic matters as CuPC(200 Å), NPB(500Å), emitting layer (300 Å), Alq₃(200 Å), LiF(5 Å), and Al(1000 Å) aredeposited on the ITO glass.

When about 1 mA of electric current is flown, brightness is about 1.8cd/A, whereby CIE (Commision Internationale de L′Eclairage) x=0.15,y=0.196.

Accordingly, the present invention is a blue emitting material of anemitting layer and an organic elecroluminescent device with blue colorpurity and a high luminescent efficiency is obtained by material withhigh color purity.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the inventions. Thus, itis intended that the present invention covers the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

What is claimed is:
 1. An organic electroluminescent material,comprising; a blue emitting material comprising; a) a dopant representedby a formula 1

wherein each of A₁ and A₂ is one of the following formulas

or wherein A₁ is one formula of the following two groups X and Y, A₂ isone formula of the following two groups X and Y, and A₁ and A₂ are thesame or different from each other

and b) a host represented by one of the following formulas


2. The organic electroluminescent material of claim 1, comprising; thedopant represented by one of the following formulas


3. A blue organic electroluminescent device, comprising: a firstelectrode and a second electrode; an organic emitting layer comprising;a) a dopant represented by a following formula 1

wherein A₁ and A₂ are selected from a substituted or non-substitutedbiphenyl, a substituted or non-substituted pyridyl, a substituted ornon-substituted naphthyl, a substituted or non-substituted quinolyl, asubstituted or non-substituted isoquinolyl, a substituted ornon-substituted fluorenyl, a substituted or non-substituted terphenyl,methyl, ethyl, propyl, propyl, and t-butyl; wherein a substituent ofeach substituted A₁ and A₂ is one selected from methyl, ethyl, propyl,i-propyl, t-butyl, cyclohexyl, methoxy, ethoxy, propoxy, butoxy,dimethylamino, trimethylsilyl, fluorine, chlorine, phenoxy, tolyoxy,dimethylamino, diethylamino, dithylamino, diphenylamino, andtriphenylsilyl b) a host represented by a following formula 2B1-X—B2 wherein the X is selected from a group consisting ofnaphthalene, phenanthrene, pyrene, perylene, and quinoline, wherein theB1 and B2 are selected from phenyl, pyridyl, naphthyl, tritolylphenyl,biphenylenyl, anthryl, phenanthryl, pyrenyl, perylenyl, quinolyl,isoquinolyl, fluorenyl, terphenyl, tolyl, xylyl, methylnaphthyl, andhydrogen.
 4. The blue organic electroluminescent device of claim 3,wherein wt. % of the material of the chemical formula 1 is 0.1-49.9 wt.% of a total weight of the organic emitting layer, the organic emittinglayer having a plurality of materials and being the blue emittingmaterial using the chemical formula 1 as the dopant.